In aeronautics, it is important to be able to determine the existence of a fuel leak in the fuel supply circuit of the engines. The presence of an undetected fuel leak may cause problems for the flight plan of the aircraft, especially when the aircraft is flying in a zone distant from any diversion airport. To resolve this problem, most aircraft are equipped with an automatic fuel leak detection system. This system has gauges, each situated in a fuel tank of the aircraft and enabling the measurement at all times of the quantity of fuel on board. The system also comprises a flowmeter for each engine by which it is possible to know the flow rate of the fuel entering the engine and, from this information, deduce the quantity of fuel consumed by each engine. A comparison of a first value of consumption computed from the variation in the quantity of fuel on board since the beginning of the flight (given by the gauges of the aircraft) with the second consumption value computed from engine flowmeters from the beginning of the flight (the sum of all the engines) enables detection of the presence of a fuel leak. In other words, this system determines the difference between the first consumption value and the second consumption value. This difference should be zero. If this difference is not zero, it means that there is a fuel leak on board the aircraft.
However, this system can be used to determine a leak in the fuel supply system, solely upstream to the flowmeter, i.e. between the fuel tanks and the flowmeters of the engines. It therefore cannot be used to determine a leak for the rest of the piping systems situated downstream from the flowmeter.
Furthermore, this system enables the detection solely of the presence of a leak. It cannot be used to locate the leak. The locating of the leak is done sequentially by an operational procedure in flight. It is done by carrying out a part-by-part isolation of the aircraft fuel supply circuit.